A processing environment has a finite number of resources to be used in scheduling jobs to be executed within the processing environment. In some environments, there are significant costs associated with allocating and deallocating resources used by the jobs, while there are relatively minor costs associated with reusing those resources without deallocating/reallocating the resources. One example of such an environment is the Blue Gene system, offered by International Business Machines Corporation, Armonk, N.Y.
In the Blue Gene system, jobs are scheduled to execute on entities called blocks. The operation of allocating a block involves physically booting the underlying Blue Gene hardware associated with the block. This is a costly operation that can take several minutes to complete. Similarly, deallocating a block involves shutting down the associated Blue Gene hardware and it is also costly. Reusing the block, on the other hand, is relatively inexpensive compared to the allocation/deallocation costs.
It is not always possible, however, to reuse a block, since blocks do not always match resource requirements of jobs being scheduled. When scheduling a job, it can either execute on a reusable block, if it matches the job's resource requirements or on a new block. In some cases, there are not enough resources available to allocate a new block. In these cases, it is necessary to deallocate some reusable blocks in order to make room for a new block to be allocated.
Currently, there are techniques used for deallocating resources and for scheduling jobs using those resources. However, those techniques are inefficient and costly.